Wireless communication systems are well known in the art. Generally, such systems comprise communication stations, which transmit and receive wireless communication signals between each other. Depending upon the type of system, communication stations typically are one of two types: base stations or wireless transmit/receive units (WTRUs), which include mobile units.
The term base station as used herein includes, but is not limited to, a base station, Node B, site controller, access point or other interfacing device in a wireless environment that provides WTRUs with wireless access to a network with which the base station is associated.
The term WTRU as used herein includes, but is not limited to, a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. WTRUs include personal communication devices, such as phones, video phones, and Internet ready phones that have network connections. In addition, WTRUs include portable personal computing devices, such as PDAs and notebook computers with wireless modems that have similar network capabilities. WTRUs that are portable or can otherwise change location are referred to as mobile units.
Typically, a network of base stations is provided where each base station is capable of conducting concurrent wireless communications with appropriately configured WTRUs. Some WTRUs are configured to conduct wireless communications directly between each other, i.e., without being relayed through a network via a base station. This is commonly called peer-to-peer wireless communications. WTRUs can be configured for use in multiple networks with both network and peer-to-peer communications capabilities.
One type of wireless system, called a wireless local area network (WLAN), can be configured to conduct wireless communications with WTRUs equipped with WLAN modems that are also able to conduct peer-to-peer communications with similarly equipped WTRUs. Currently, WLAN modems are being integrated into many traditional communicating and computing devices by manufacturers. For example, cellular phones, personal digital assistants (PDAs), consumer electronics (CEs), and laptop computers are being built with one or more WLAN modems.
An example of a wireless local area network environment with one or more WLAN access points (APs) is a WLAN built according to the IEEE 802.11 standard. Access to these networks usually requires user authentication procedures. Protocols for such systems continue to be standardized in the WLAN technology area. One such framework of protocols is the IEEE 802 family of standards. In addition to the WLAN 802.11 standard, these include, but are not limited to, the 802.15 WPAN (Wireless Personal Area Networks) implemented with, for example, Bluetooth devices, and 802.16 WMAN (Wireless Metropolitan Area Networks).
The basic service set (BSS) is the basic building block of an IEEE 802.11 LAN and is comprised of WTRUs referred to as stations (STAs). Basically, a set of STAs which can communicate with each other can form a BSS. Multiple BSSs are interconnected through an architectural component, called a distribution system (DS), to form an extended service set (ESS). An access point (AP) is a STA that provides access to the DS by providing DS services and generally allows concurrent access to the DS by multiple STAs.
There are two prevalent ways to implement wireless communications in WLAN and other networks: 1) an infrastructure mode; and 2) an ad hoc mode. FIG. 1A illustrates an infrastructure mode, where WTRUs conduct wireless communications via a base station 54 that serves as an access point to network infrastructure 16. The base station 54 is shown as conducting communications with WTRU 18, WTRU 20, WTRU 22, WTRU 24, and WTRU 26. There are no direct intercommunications between the WTRUs illustrated in FIG. 1A. The communications are coordinated and synchronized through the base station 54. Such a configuration is also called a basic service set (BSS) within WLAN contexts.
In contrast to the infrastructure mode, the ad hoc mode does not use network infrastructure. The ad hoc mode operates with peer-to-peer communications and is also called “independent BSS”. In ad hoc mode, two or more WTRUs establish a communication among themselves without the need of a coordinating network element, i.e., base station. Ad hoc mode operation is illustrated in FIG. 1B. No access points to the network infrastructure are required. However, a base station can be configured with the ad hoc protocols to act as the other WTRUs in peer-to-peer communications. In such case, a base station may act as a bridge or a router to another network or to the Internet.
Where a base station does join an ad hoc network, it is treated as another WTRU and does not normally control the flow of communication. For example, FIG. 1B illustrates base station 54 in communication with WTRU 18 and WTRU 18 in communication with WTRU 20 in an ad hoc network. In this scenario, the base station 54 does not control the flow of data.
Communications are normally limited to the other stations in an ad hoc network, but one WTRU may communicate indirectly with another WTRU via a third WTRU serving as a relaying node. For example, as shown in FIG. 1B, where both WTRU 22 and WTRU 24 are communicating in ad hoc mode with WTRU 26, communications may occur between WTRU 22 and WTRU 24. Additionally, when a WTRU is in ad hoc mode, it typically ignores infrastructure mode base station transmissions. It is also necessary for one WTRU to initiate ad hoc mode and other WTRUs to join in. The other stations will assimilate the operating parameter information as they join the ad hoc network.
The station that starts an ad hoc network selects the ad hoc network's operating parameters, such as the service set identifier (SSID), channel and beacon timing, and then transmits this information in, for example, beacon frames. As stations join the ad hoc network, they assimilate the operating parameters. In infrastructure mode, parameters such as the SSID are normally specified by a network controller connected to network base stations.
The SSID in an IEEE 802 based system can be a 32-character unique identifier attached to a header of packets sent over a WLAN. The SSID differentiates logically one WLAN from another, so all base stations and all devices attempting to connect to a specific WLAN normally use the same SSID.”
In an IEEE 802 based system, once more than one station is part of an ad hoc network, all of the stations share the burden of sending beacon frames by a random distribution of that task to each station. Algorithms such as the spokesman election algorithm have been designed to “elect” one device as a master station (i.e., pseudo base station) of the ad hoc network with all others being slaves.
When a plurality of ad hoc networking WTRUs communicate with each other a mesh network is created. Accordingly, mesh networks are a type of ad-hoc network where more than one WTRU communicates directly or indirectly with at least two other WTRUs in the mesh. From a strict IEEE 802.11 group point of view as Ad-hoc network allows WTRUs to communicate to whichever WTRU they want “directly” over the same shared medium, whereas the Mesh network allows WTRUs to communicate “directly or indirectly” over one or more media. That is, ad-hoc WTRUs can only talk to WTRUs within their radio reach, and mesh WTRUs can forward or relay information from two other different WTRUs allowing these other WTRUs to communicate with each other, even if they are not within each others transmission range, if they are not in the same band, or if they do not use the same physical layer (e.g. 802.11a and 802.11b). This distinction is not limiting in the context of the present invention.
The inventors have recognized that in communication systems, there are different ways to optimize operation performance through system reconfigurations. These reconfigurations are the outcome of decisions that are usually based on system status, predictions, etc. and follow the rules of certain procedures or algorithms. When information about the system cannot be centralized in a single point, distributed decisions or algorithms are the only way to overcome the problem. Due to the nature of mesh networks, distributed decisions are often used as a single solution. Although the decision could be sub-optimal, no other alternative can be taken.